1. Field
The present invention relates generally to a technique for updating an encryption/decryption key used in a block cipher algorithm.
2. Background
Differential power analysis (DPA) attacks are becoming more prevalent because data collection and analysis is becoming relatively cheap to perform with modern equipment. A DPA attack is a statistical side-channel attack that deduces a secret key. Techniques for countering a DPA attack may involve power supply filtering, random noise insertion, key “masking”, or key rolling techniques. Some of such techniques may be computationally intensive or otherwise may prove to be impractical.
A technique disclosed in U.S. Pat. No. 8,386,800 is based on a ciphertext hash chaining process using a hash function to provide a rolling key for defeating a DPA attack. However, the hash function may be costly in processing time, system resources, and/or device circuitry.
There is therefore a need for a key update technique for use in a block cipher algorithm to thwart an attack such as a DPA attack.